Coal haulage systems have been available for use in coal mines to receive coal fragments presently being mined by a coal mining machine, and to carry that coal, by a belt conveyer, through substantially horizontal shafts. Modern coal mining machines include their own integral, flexible belt conveyor to continuously remove coal from the cutting area.
The coal from the above mining machine typically is transported to another conveyor system which has means to receive the coal from the conveyor of the mining machine, and further means to transport the coal through one section of the conveyor and to other downstream sections. A mobile type of bridge conveyor is disclosed in U.S. Pat. No. 4,031,997 (by Nelson). In Nelson, each of the bridge conveyors is wheeled and is configured to either receive coal from the mining machine, or to dump the coal into some other system (such as an elevator). Between the bridge conveyors are intermediate mobile conveyors, which are also wheel-mounted. The intermediate conveyors have inbye and outbye ends, of which the inbye ends use a pair of side rails to carry a dolly. The dolly has "V"-grooved wheels which mate to the rails, so that the dolly may move longitudinally along the intermediate conveyer. The dolly helps to receive the coal from one section of the conveyer such that the coal is directed onto the conveyor belt before further transportation toward another intermediate section, or to the final bridge conveyer.
Each of the rails that receives the "V"-grooved wheels is further supported by a generally vertical frame structure, which supports the weight of the dolly. This type of vertical frame arrangement is typical for coal mining conveyor systems.
Another type of conveyor system that uses "V"-grooved wheels is disclosed in U.S. Pat. No. 4,754,864 (by Cross). Cross discloses a conveyor that feeds material into a blending bin having a horizontal frame along its longitudinal axis. The V-grooved wheels are mated to a track member which is supported by a vertical frame member, also running along the longitudinal axis. In Cross, the V-grooved wheels allow the longitudinal movement of a gantry blade and diverter discharge device.
The existing coal haulage systems that use a dolly guided by a pair of rails all use some type of vertical frame structure to support the weight of the dolly. Because of this fact, such coal haulage systems are greater in vertical height than if the vertical frame sections were eliminated from the structure.
Existing coal haulage systems comprising of sections of track to support the dolly are difficult in joining one section to its adjacent section. The vertical frame which supports the rails typically has a male end which must fit inside a mating female end of its adjacent section. In such sectional coal haulage systems, the tolerance is relatively tight as to the clearance between the outer portions of the male mating member and the inner portions of the female mating member. The alignment of the holes for such screws or bolts is quite difficult when situated within an actual coal mine.